JP2013242547A - Optical scanner, and image forming apparatus including the optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform light amount control with high accuracy by direct contact of a heat flow generated by rotation of a rotary polygon mirror 202 with a lens 215 disposed between a beam splitter 210 and a PD 211.
A wall is provided between a region where a rotating polygon mirror 202 and a motor are arranged and a region where a lens is arranged.
[Selection] Figure 6

Description

  The present invention relates to an optical scanning device that emits a light beam that scans a photosensitive member, and an image forming apparatus including the optical scanning device.

  An image forming apparatus such as an electrophotographic copying machine and a printer develops an electrostatic latent image formed on a photosensitive member by exposing the photosensitive member with a light beam such as a laser beam to develop an image with toner. Form. An optical scanning device is used as a device for emitting laser light for exposing a photosensitive member.

  The optical scanning device converts a light beam from a semiconductor laser as a light source into a substantially parallel light beam, and then deflects the light beam with a rotating polygon mirror (polygon mirror) or the like. The light beam deflected by the rotating polygon mirror scans the photoreceptor in a substantially straight line.

  Recent optical scanning apparatuses expose a photosensitive member with a plurality of laser beams emitted from a plurality of light emitting points in order to cope with an increase in image forming speed and a resolution of an image. In particular, a vertical cavity surface emitting laser (hereinafter referred to as a VCSEL) is easily arrayed with a large number of light emitting points, and is proposed to be used as a light source for an optical scanning device. .

  In the optical scanning device, the light amount of the light beam emitted from the light source is detected by an optical sensor, and the light amount of the light beam emitted from the light source is controlled based on the detected light amount. Unlike an edge emitting semiconductor laser, a VCSEL does not have a back laser beam corresponding to a light beam guided to a photoconductor. Therefore, in order to control the amount of light beam emitted from the VCSEL, a part of the light beam emitted toward the photosensitive member is separated by a beam splitter or the like, and one separated light beam is separated by a rotating polygon mirror. There has been proposed an optical scanning device that deflects and guides it onto a photosensitive member, and detects the amount of light by guiding the other light beam to an optical sensor (see Patent Document 1). The light amount ratio between the light amount of the light beam that passes through the beam splitter and is guided to the photosensitive member and the light amount of the light beam that is guided to the optical sensor is uniquely determined by the reflectance of the beam splitter. Therefore, the light amount of the light beam reaching the photosensitive member can be controlled to the target light amount by controlling the light amount of the light beam emitted from the VCSEL according to the received light amount of the optical sensor.

JP 2006-91157 A

  However, the motor that rotates the rotary polygon mirror during image formation becomes a heat source, and the following problems occur. That is, when the rotating polygon mirror rotates, an air flow is generated toward the radially outer side of the rotating polygon mirror. The airflow is heated by the heat generated by the motor, and this airflow directly hits the optical sensor and the lens disposed between the beam splitter and the optical sensor. As a result, fluctuations in the optical characteristics (refractive index, etc.) of the lens and fluctuations in the installation position due to thermal deformation of the lens installation position may occur, and the optical path of the light beam from the beam splitter toward the optical sensor may be changed. . If an optical sensor having a light receiving area that strongly requires fluctuations in the optical path of the light beam is used, it becomes impossible to perform highly accurate light quantity control that increases the cost of the optical sensor. The present invention provides an optical scanning device capable of performing light amount control with high accuracy while suppressing optical path fluctuations of a light beam traveling from a beam splitter to an optical sensor.

  The present invention has been made in view of the above problems, and an optical scanning device of the present invention includes a light source that emits a light beam, a light beam emitted from the light source, a first light beam, and a second light beam. A beam splitter for separating the first light beam, a rotary polygon mirror for deflecting the first light beam so that the first light beam separated by the beam splitter scans on a photosensitive member, and the rotary polygon mirror is driven to rotate. A first lens for guiding the first light beam deflected by the rotary polygon mirror to the photoconductor, an optical sensor for receiving the second light beam reflected by the beam splitter, The light beam incident on the beam splitter is disposed on a line segment that is opposite to the first lens with respect to the light beam of the light beam and that connects the beam splitter and the optical sensor. The second light beam separated by the beam splitter is incident, the second lens that focuses the incident second light beam on the optical sensor, the beam splitter, the first lens, the An optical box in which the rotary polygon mirror, the motor, the optical sensor, and the second lens are arranged, and the optical box includes an area in which the rotary polygon mirror and the motor are arranged and the second box. A wall standing from the bottom surface of the optical box between the lens and the region where the lens is disposed, and the height of the wall from the bottom surface of the optical box is higher than the height from the bottom surface of the optical box to the rotary polygon mirror It is also characterized by high. The optical scanning device according to the present invention includes a light source that emits a light beam, a beam splitter that separates the light beam emitted from the light source into a first light beam and a second light beam, and the beam splitter. The separated first light beam is deflected by a rotating polygon mirror that deflects the first light beam so as to scan on the photosensitive member, a motor that rotationally drives the rotating polygon mirror, and the rotating polygon mirror. A first lens that guides the first light beam to the photosensitive member, an optical sensor on which the second light beam reflected by the beam splitter is incident, and a light source that is emitted from the light source and incident on the beam splitter. The light beam is disposed on the opposite side of the first lens with respect to the light beam and on a line segment connecting the beam splitter and the optical sensor. A second lens for allowing the second light beam separated by the splitter to be incident thereon and condensing the incident second light beam on the optical sensor; the beam splitter; the first lens; An optical box in which the mirror, the motor, the optical sensor, and the second lens are disposed, and the optical box includes an area in which the rotary polygon mirror and the motor are disposed and the second lens. It is provided with the wall which stood up from the bottom face of the said optical box between the area | regions arrange | positioned, and opposes the reflective surface of the said rotary polygon mirror.

  According to the present invention, a wall having a height from the bottom surface of the optical box higher than the height of the rotary polygon mirror is provided between the area where the rotary polygon mirror and the motor are arranged and the area where the lens is arranged. Therefore, the optical path fluctuation of the light beam traveling from the beam splitter to the optical sensor can be suppressed.

Schematic sectional view of a color image forming apparatus Perspective view and top view of optical scanning device Sectional view of optical scanning device and main part configuration diagram Exploded perspective view of the optical unit Control block diagram of optical scanning device Timing chart for explaining light control timing Enlarged view of perspective view and top view of optical scanning device The figure which shows the temperature change of the area | regions A, B, and C in an optical box Figure showing a modification

Example 1
FIG. 1 is a schematic cross-sectional view of a digital full-color printer (color image forming apparatus) that forms an image using a plurality of color toners. 2A and 2B are a perspective view (a), a top view (b), a cross-sectional view (c), and a main part of an optical scanning device which is a light beam emitting device provided in the digital full-color copying machine shown in FIG. It is a part block diagram (d). In addition, although an Example demonstrates a color image forming apparatus and the optical scanning device with which it is provided as an example, embodiment is not restricted to a color image forming device and the optical scanning device with which it is provided, but a monochromatic toner (for example, An image forming apparatus that forms an image only with black) and an optical scanning device provided in the image forming apparatus may be used.

  First, the image forming apparatus 100 of this embodiment will be described with reference to FIG. The image forming apparatus 100 includes four image forming units (image forming units) 101Y, 101M, 101C, and 101Bk that form images according to colors. Here, Y, M, C, and Bk represent yellow, magenta, cyan, and black, respectively. The image forming units 101Y, 101M, 101C, and 101Bk perform image formation using toners of yellow, magenta, cyan, and black, respectively.

  The image forming units 101Y, 101M, 101C, and 101Bk are provided with photosensitive drums 102Y, 102M, 102C, and 102Bk that are photosensitive members. Around the photosensitive drums 102Y, 102M, 102C, and 102Bk, charging devices 103Y, 103M, 103C, and 103Bk, optical scanning devices 104Y, 104M, 104C, and 104Bk, and developing devices 105Y, 105M, 105C, and 105Bk are provided, respectively. . In addition, drum cleaning devices 106Y, 106M, 106C, and 106Bk are disposed around the photosensitive drums 102Y, 102M, 102C, and 102Bk.

  An endless belt-like intermediate transfer belt 107 is disposed below the photosensitive drums 102Y, 102M, 102C, and 102Bk. The intermediate transfer belt 107 is stretched around a driving roller 108 and driven rollers 109 and 110, and rotates in the direction of arrow B in FIG. 1 during image formation. In addition, primary transfer devices 111Y, 111M, 111C, and 111Bk are provided at positions facing the photosensitive drums 102Y, 102M, 102C, and 102Bk via the intermediate transfer belt 107 (intermediate transfer member).

  Further, the image forming apparatus 100 of the present embodiment includes a secondary transfer device 112 for transferring the toner image on the intermediate transfer belt 107 to the recording medium S, and a fixing device 113 for fixing the toner image on the recording medium. Prepare.

  Here, an image forming process from the charging process to the developing process of the image forming apparatus 100 having such a configuration will be described. Since the image forming process in each image forming unit is the same, the image forming process will be described using the image forming unit 101Y as an example, and the description of the image forming processes in the image forming units 101M, 101C, and 101Bk will be omitted.

  First, the photosensitive drum 102Y that is rotationally driven by the charging device of the image forming unit 101Y is charged. The charged photosensitive drum 102Y (on the image carrier) is exposed by laser light emitted from the optical scanning device 104Y. As a result, an electrostatic latent image is formed on the rotating photoconductor. Thereafter, the electrostatic latent image is developed as a yellow toner image by the developing device 105Y.

  Hereinafter, the image forming process after the transfer process will be described using the image forming unit as an example. The yellow, magenta, cyan, and black toner images formed on the photosensitive drums 102Y, 102M, 102C, and 102Bk of the image forming units when the primary transfer devices 111Y, 111M, 111C, and 111Bk apply a transfer bias to the transfer belt. Are respectively transferred to the intermediate transfer belt 107. As a result, the toner images of the respective colors are superimposed on the intermediate transfer belt 107.

  When the four-color toner image is transferred to the intermediate transfer belt 107, the four-color toner image transferred onto the intermediate transfer belt 107 is transferred from the manual feed cassette 114 or the paper feed cassette 115 by the secondary transfer device 112. Transfer (secondary transfer) is performed again on the recording medium S conveyed to the next transfer portion T2. Then, the toner image on the recording medium S is heated and fixed by the fixing device 113 and discharged to the paper discharge unit 116, and a full color image is obtained on the recording medium S.

  The photosensitive drums 102Y, 102M, 102C, and 102Bk that have been transferred have their residual toner removed by the drum cleaning devices 106Y, 106M, 106C, and 106Bk, and then the above-described image forming process continues.

  Next, the configuration of the optical scanning devices 104Y, 104M, 104C, and 104Bk will be described with reference to FIG. 2, FIG. 3, and FIG. Since the configuration of each optical scanning device is the same, subscripts Y, M, C, and Bk indicating colors are omitted in the following description. The optical scanning device 104 includes an optical box 201, and various optical members described below are arranged inside the optical box 201.

  2A (a) is a perspective view of the optical scanning device 104, FIG. 2A (b) is a top view of the optical scanning device 104, FIG. 2B (c) is a cross-sectional view of AA ′ in FIG. 2B (b), and FIG. (D) is the perspective view which showed the structure of the main optical components. As shown in FIG. 2A (a), an optical unit 200 described later is attached to the optical box 201. Inside the optical box 201, there is provided a rotating polygon mirror 202 which is a deflecting means for deflecting the laser light emitted from the optical unit so that the laser light scans the photosensitive drum in a predetermined direction. The rotary polygon mirror 202 is rotationally driven by a motor 203 shown in FIG. 2B (c). The laser light deflected by the rotating polygon mirror 202 is incident on the first fθ lens 204 (first lens). The first fθ lens 204 is positioned by a positioning portion 219 provided on the incident surface side on which the laser light is incident. The laser light that has passed through the first fθ lens 204 is reflected by the reflection mirror 205 and the reflection mirror 206 (see FIGS. 2B (c) and 2 (d)) and enters the second fθ lens 207. The laser light that has passed through the second fθ lens 207 is reflected by the reflection mirror 208, passes through the dustproof glass 409, and is guided onto the photosensitive drum. Laser light scanned at a constant angular velocity by the rotary polygon mirror 202 forms an image on the photosensitive member by the first fθ lens 204 and the second fθ lens 207 and scans the photosensitive member at a constant velocity.

  The optical scanning device 104 of this embodiment includes a beam splitter 210 that is a light beam separating unit. The beam splitter 210 is disposed on the optical path of laser light emitted from the optical unit 200 and directed to the rotary polygon mirror 202. In this embodiment, the beam splitter 210 is disposed between the optical unit 200 and the rotary polygon mirror 202. The laser light incident on the beam splitter 210 is separated into first laser light (first light beam) that is transmitted light and second laser light (second light beam) that is reflected light.

  FIG. 6A is an enlarged perspective view of a portion where the beam splitter 210 is disposed, and FIG. 6B is a top view thereof. As shown in FIG. 6B, the beam splitter 210 has an entrance surface 210a and an exit surface 210b, and a coating (film) is formed on the entrance surface 210a so as to have a constant reflectance (transmittance). ing. Even if the exit surface 210b undergoes internal reflection, a slight angular difference with respect to the entrance surface 210a is provided so that the laser light reflected by the internal surface is guided in a different direction from the second laser light reflected by the entrance surface 210a. Have. That is, the entrance surface 210a and the exit surface 210b are not parallel. Further, the second laser light reflected by the incident surface 210 a of the beam splitter 210 is guided to the opposite side of the first fθ lens 204 with respect to the light beam of the laser light emitted from the optical unit 200 and directed to the rotary polygon mirror 202.

  The first laser beam is deflected by the rotary polygon mirror 202 and guided to the photosensitive drum as described above. The second laser light passes through a condenser lens 215 (second lens) shown in FIG. 2A (a), and then enters a photodiode 211 (hereinafter, PD 211) that is an optical sensor (light receiving unit). An opening is provided in the side wall of the optical box 201, and the condenser lens 215 is disposed on a line segment connecting the PD 211 and the beam splitter 210. The PD 211 is attached to this opening from the outside of the optical box 201. The second laser light that has passed through the condenser lens 215 passes through the opening and enters the PD 211. In order to reduce the size and cost of the optical scanning device 104, no reflecting mirror is disposed on the optical path of the second laser beam. The PD 211 outputs a detection signal corresponding to the amount of received light, and automatic light control (APC) described later is performed based on the output detection signal. Note that the PD 211 may be provided inside the optical box 201.

  Further, the optical scanning device 104 of this embodiment includes a Beam Detector 212 (hereinafter referred to as BD 212) that generates a synchronization signal for determining the emission timing of laser light based on image data on the photosensitive drum. As shown in FIG. 2B (d), the laser light (first laser light) deflected by the rotary polygon mirror 202 passes through the first fθ lens 204, is reflected by the reflection mirror 205, and the reflection mirror 214, Incident on BD212.

  Since the optical box 201 has a shape with open surfaces at the top and bottom, as shown in FIG. 2B (c), the optical box 201 is attached with an upper lid 217 and a lower lid 218, and the inside is sealed.

  FIG. 3 is an exploded perspective view of the optical unit 200 attached to the housing of the optical scanning device 104. FIG. 3A is a perspective view seen from the lens barrel side described later, and FIG. 3B is a perspective view seen from the substrate side described later.

  The optical unit 200 is a semiconductor laser 302 (for example, a vertical cavity surface emitting laser) that is a light source that emits a laser beam (light beam) and an electric for driving the semiconductor laser 302. A substrate 303 (hereinafter referred to as a substrate 303) is provided. Hereinafter, the semiconductor laser 302 will be described as the VCSEL 302. As shown in FIG. 3A, the VCSEL 302 is mounted on the substrate 303.

  The laser holder 301 includes a lens barrel portion 304, and a collimator lens 305 is attached to the tip of the lens barrel portion 304. The collimator lens 305 converts laser light (diverged light) emitted from the VCSEL 302 into parallel light. The collimator lens 305 is adjusted in its installation position on the laser holder 301 while detecting the irradiation position and focus of the laser light emitted from the VCSEL 302 with a specific jig when the optical scanning device 104 is assembled. When the installation position of the collimator lens 305 is determined, the collimator lens 305 is bonded and fixed to the laser holder 301 by irradiating the ultraviolet curable adhesive applied between the collimator lens 305 and the lens barrel 304 with ultraviolet rays. Is done. The VCSEL 302 is electrically connected to the substrate 303, and the VCSEL 302 emits laser light by a drive signal supplied from the substrate 303.

  Next, a method for fixing the substrate 303 on which the VCSEL 302 is mounted to the laser holder 301 will be described. In FIG. 3, a substrate support member 307 for fixing the substrate 303 to the laser holder 301 is made of an elastic material. As shown in FIG. 3A, the substrate support member 307 includes three screw holes (fixed portions) that are screwed into the screws 309 and three openings that allow the screws 308 to pass therethrough. The screw 309 passes through the hole provided in the substrate 303 and is screwed into the screw hole provided in the substrate support member 307. Further, the screw 308 passes through the opening of the substrate support member 307 and is screwed into a screw hole provided in the laser holder 301.

  When assembling the optical unit, first, the substrate support member 307 is fixed to the laser holder 301 with screws 308. Next, the VCSEL 302 mounted on the substrate 303 is pressed against three abutting portions 301 a (see FIG. 3B) provided on the laser holder 301. There is a gap between the substrate support member 307 and the substrate 303. Next, by fastening the screw 309, the substrate support member 307 is elastically deformed into an arcuate shape with the laser holder 301 projecting. The substrate 303 is pressed against the abutting portion 301 a by the restoring force, and the VCSEL 302 is fixed to the laser holder 301.

  FIG. 4 is a control block diagram of the image forming apparatus according to the present exemplary embodiment. Since the components in the image forming units for the respective colors in the present embodiment are the same, a control block diagram of the image forming unit 101Y will be described below as an example.

  The CPU 401 is a control unit that causes each element to execute predetermined control based on a control program stored in the memory 402. The process unit shown in FIG. 5 is a generic term for a drive unit that drives a photosensitive drum, a charging device 103Y, a developing device 105Y, a drum cleaning device 106Y, a drive roller 108, and a primary transfer device 111Y. Description is omitted. In addition, the CPU 401 controls the secondary transfer device 112 and the fixing device 113 for fixing the toner image on the recording medium S, but a detailed description of the control is omitted.

  In addition to the control program, the memory 402 stores reference value data used when executing APC and timing data that defines the emission timing of each light emitting element. The CPU 401 includes a clock signal generation unit such as a crystal oscillator that generates a clock signal having a frequency higher than that of the synchronization signal, and a counter that counts the clock signal.

  A synchronization signal output from the BD 212 is input to the CPU 401. Further, the detection signal output from the PD 211 is input to the CPU 401. The CPU 401 transmits a control signal to the laser driver 403 based on the synchronization signal, and the laser driver 403 transmits a drive signal to the VCSEL 302 based on the control signal.

  Hereinafter, the control performed in one scanning period in which laser light is scanned once in this embodiment will be described with reference to FIG.

  In FIG. 5, (1) shows a synchronization signal (BD signal) from the BD 212, (2) shows a drive signal transmitted from the laser driver 403 to the light emitting element A among the plurality of light emitting elements of the VCSEL 302, 3) shows a drive signal transmitted from the laser driver 403 to the light emitting element B among the plurality of light emitting elements of the VCSEL 302. For the sake of simplicity, only the light emitting elements A and B are shown, but the number of light emitting elements may be three or more.

  As shown in (2) of FIG. 5, the laser driver 403 transmits a drive signal to the light emitting element A in accordance with the timing at which the light beam from the light emitting element A enters the BD 212 in order to generate a synchronization signal. In response to the drive signal, laser light is emitted from the light emitting element A, and the BD 212 receiving the laser light generates a synchronization signal.

  The CPU 401 determines the exposure start position (image formation start position) in the main scanning direction based on the generation timing of the synchronization signal. The CPU 401 responds when the count value counted in response to the generation of the synchronization signal becomes the first predetermined value (one of the timing data) set corresponding to each light emitting element. The laser driver 403 starts emitting laser light based on the image data. That is, as shown in (2) and (3) of FIG. 5, the CPU 401 forms a toner image on the photosensitive drum after predetermined times T11 and T12 (sec) corresponding to the first predetermined value after the synchronization signal is generated. The laser driver 403 starts to emit laser light for formation. Thereafter, laser light based on the image data is emitted from the light emitting elements A and B in the latent image formation period of (2) and (3) in FIG. In the optical scanning device of this embodiment, the imaging position of the laser light emitted from the light emitting element A and the imaging position of the laser light emitted from the light emitting element B are in the scanning direction in which the laser light scans the photosensitive member ( In the main scanning direction). Therefore, the time from when the synchronization signal is generated until the light emitting element A emits the laser light based on the image data is T11, and the light emitting element B emits the laser light with a delay of (T11-T12) from T11. Has been.

  The CPU 401 resets the count value of the counter in response to the generation of the synchronization signal and starts counting. Then, in response to the count value of the counter reaching the second predetermined value (one of the timing data) set in correspondence with each light emitting element, the CPU 401 changes each light emitting element of the VCSEL 302. APC of each light emitting element is executed based on the light reception result of individually turning on and receiving the laser light emitted from each light emitting element. That is, as shown in FIG. 5, the CPU 401 executes APC after predetermined times T21 and T22 (sec) corresponding to the second predetermined value after the synchronization signal is generated. APC is executed during the APC execution period shown in FIG.

  Note that the first predetermined value and the second predetermined value set corresponding to each of the light emitting elements described above are based on the rotational speed of the rotary polygon mirror, and the laser light scanned on the rotary polygon mirror is BD212, PD211. Is set based on the timing at which the light enters.

  The CPU 401 compares the voltage of the detection signal output from the PD 211 with a reference voltage corresponding to the target light amount (corresponding to reference data stored in the memory 402), and supplies the light to each light emitting element based on the voltage difference. A drive current value as a signal is controlled. That is, when the voltage of the detection signal output from the PD 211 is lower than the voltage corresponding to the target light amount, the drive current supplied to the light emitting element is increased to increase the light amount of the laser light. On the other hand, when the voltage of the detection signal output from the PD 211 is higher than the voltage corresponding to the target light amount, the current supplied from the laser driver 403 to the light emitting element is decreased to reduce the light amount of the laser light.

  Next, features of the optical scanning device in the present embodiment will be described with reference to FIG. 2B (c) and FIG. When the rotary polygon mirror 202 rotates, the motor 203 generates heat. When the rotating polygonal mirror 202 rotates, an air flow is generated toward the radially outer side of the rotating polygonal mirror 202. When this heated airflow directly hits the condenser lens 215 and the PD 211, the optical characteristics (refractive index, etc.) of the condenser lens 215, changes in the installation position, the photoelectric conversion characteristics of the PD 211, and the like change.

  When the optical characteristics and the installation position of the condenser lens 215 change and the optical path of the second laser light changes, the laser light deviates from the light receiving surface of the PD 211. If PD 211 having a large area of the light receiving surface is used so that laser light is reliably imaged on the light receiving surface of PD 211, the cost increases. Further, when the laser beam deviates from the light receiving surface of the PD 211, the amount of the second laser beam incident on the PD 211 is reduced even if the amount of the laser beam emitted from the light emitting element of the VCSEL 302 is appropriate. Controls to increase the light quantity of the light emitting element of the VCSEL 302. Further, when the temperature of the PD 211 rises, the internal resistance value of the PD 211 may fluctuate and the output value from the PD 211 to the CPU 401 may deviate from the true value.

  Therefore, as shown in FIG. 6A, a wall standing from the bottom surface of the optical box 201 between the area where the rotating polygon mirror 202 is arranged and the area where the condenser lens 215 is arranged in the optical box 201. 216 is provided. The wall 216 is a member formed integrally when the optical box 201 is molded. The wall 216 extends from the outer wall (side wall) of the optical box 201 toward the inside of the optical box 201, and includes an area A where the rotary polygon mirror 202 and the motor 203 are disposed, a condensing lens 215, and a PD 211 (opening on the side wall). Is set up between the area B and the area B. As shown in FIG. 2B (c), the position of the upper end of the wall 216 (the height of the wall 216 from the bottom surface of the optical box 201) is higher than the upper ends of the plurality of reflecting surfaces of the rotary polygon mirror 202. That is, the wall 216 erected from the bottom surface of the optical box 201 faces at least one of the reflecting surfaces of the rotary polygon mirror 202. The reflection surface of the rotary polygon mirror 202 facing the wall 216 differs depending on the rotation phase of the rotary polygon mirror 202. Furthermore, the upper end of the wall 216 is higher than the upper end of the condenser lens 215 (the height of the condenser lens from the bottom surface of the optical box 201). Further, the upper end of the beam splitter 210 (the height of the beam splitter from the bottom surface of the optical box 201) is also higher than the positions of the plurality of reflecting surfaces of the rotary polygon mirror 202. As a result, it is possible to prevent the airflow generated by the rotation of the rotary polygon mirror 202 from directly hitting the condenser lens 215 and the PD 211. The “bottom surface of the optical box” serving as a reference for the height is the surface 201a in FIG. 2B (c). Furthermore, since the wall 216 is erected from the bottom surface, it also serves as a reinforcing portion (reinforcing rib) that reinforces the optical box 201. The wall 216 may be a separate member from the optical box 201.

  Further, the beam splitter 210 is disposed adjacent to the wall 216 in a direction parallel to the bottom surface of the optical box 201, and one end of the beam splitter 210 and the end of the wall 216 are in contact with each other in the height direction of the optical box 201. doing. As a result, the wall 216 and the beam splitter 210 separate the area where the rotating polygonal mirror 202 is arranged from the area where the condenser lens 215 and the PD 211 are arranged, and the wall 216 and the beam splitter 210 shield the airflow. It is possible to reduce the influence of the heated airflow on the condenser lens 215 and the PD 211. Further, in the direction parallel to the bottom surface of the optical box 201, as shown in FIG. 6B, the other end of the beam splitter 210 and the positioning portion 219 of the fθ lens 204 are in contact with each other in the height direction of the optical box 201. In addition, the region A and the region B are isolated from each other at the height of the plurality of reflecting surfaces of the rotary polygon mirror 202.

  The effect of the wall 216 will be described with reference to FIG. FIG. 7 shows temperature fluctuations in the region A, the region B, and the region C when the rotary polygon mirror 202 is continuously rotated. The vertical axis indicates temperature (° C.), and the horizontal axis indicates time (minutes). A region C is a point on the first fθ lens 204 to which the airflow from the rotary polygon mirror 202 directly hits, and is described for comparison. It can be seen that the temperature of the region B indicated by the alternate long and short dash line is suppressed by the presence of the wall 216 as compared with the temperature fluctuation of the region C indicated by the dotted line.

  In the above-described embodiment, the wall 216 of the optical box 201 is set higher than the condenser lens 215 in the range from the outer wall to the end face of the beam splitter 210, and the height of the portion of the beam splitter 210 is lower than that of the wall 216. However, as shown in FIG. 8, an opening (not shown) to which the beam splitter 210 is attached may be provided on the wall 216 b, and the wall 216 b may be connected to the positioning portion 219 of the fθ lens 204. That is, the wall 216b may be a connecting portion that connects the side wall of the optical box 201 and the positioning portion 219. In this case, the wall 216b is also provided on the upper side of the beam splitter 210.

  If the walls 216 and 216b are in contact with the upper lid 217, the temperature rise in the region B can be further suppressed. At this time, if the periphery of the motor 203 which is a heat generation source is completely enclosed, the heat is trapped and the optical box 201 may be deformed due to a partial temperature increase. For this reason, it is desirable that an appropriate space is ensured between the rotating polygon mirror 202 of the optical box 201 and the upper lid 217 on the opposite side of the beam splitter 210 and the upper portion of the first fθ lens 204.

  In this embodiment, a wall 216 is provided between the rotating polygon mirror 202 and the condenser lens 215, whereas a wall is provided between the rotational polygon mirror 202 and the first fθ lens 204. Not. Hot air does not flow in the region B where the condenser lens 215 is disposed by the wall 216. As a result, the temperature of the rotary polygon mirror 202 rises and the region A of the optical box 201 is deformed. On the other hand, the optical scanning device 104 of the present embodiment opens the space between the rotary polygon mirror 202 and the first fθ lens 204 to generate hot air generated by the rotation of the rotary polygon mirror 202 with the first fθ lens. It is configured to flow to the 204 side.

  As described above, by providing the wall 216 or 216b between the area where the rotary polygon mirror 202 and the motor are arranged and the area where the lens is arranged, the hot air is prevented from directly hitting the condenser lens 215. be able to. Thereby, APC can be executed even during continuous image formation.

201 Optical box 202 Rotating polygon mirror 211 Photodiode 215 Condensing lens 216 Wall

Claims (16)

A light source that emits a light beam;
A beam splitter that separates a light beam emitted from the light source into a first light beam and a second light beam;
A rotating polygon mirror for deflecting the first light beam so that the first light beam separated by the beam splitter scans on a photoreceptor;
A motor for rotationally driving the rotary polygon mirror;
A first lens for guiding the first light beam deflected by the rotary polygon mirror to the photoconductor;
An optical sensor for receiving the second light beam reflected by the beam splitter;
The light beam incident on the beam splitter is disposed on a line segment that is opposite to the first lens with respect to the light beam and that connects the beam splitter and the optical sensor, and is separated by the beam splitter. A second lens that is incident with a second light beam and that focuses the incident second light beam on the optical sensor;
An optical box in which the beam splitter, the first lens, the rotary polygon mirror, the motor, the optical sensor, and the second lens are disposed,
The optical box includes a wall erected from a bottom surface of the optical box between a region where the rotary polygon mirror and the motor are disposed and a region where the second lens is disposed, and the bottom surface of the optical box The height of the wall from is higher than the height from the bottom of the optical box to the rotary polygon mirror.   2. The optical scanning device according to claim 1, wherein the wall is a member that suppresses an airflow generated by the rotation of the rotary polygon mirror from directly hitting the second lens. 3. The beam splitter is attached to the bottom surface of the optical box,
The beam splitter in a direction parallel to the bottom surface is disposed at a position adjacent to the wall and is in contact with the wall, and the wall and the beam splitter include an area where the rotary polygon mirror and the motor are disposed. 3. The optical scanning device according to claim 1, wherein the optical scanning device separates a region where the second lens is disposed. 4.   The optical box is positioned from the optical box on the incident surface side of the first lens on which the first light beam deflected by the rotary polygon mirror is incident, and a positioning unit that positions the first lens The optical scanning device according to claim 3, wherein the other end of the beam splitter in a direction parallel to the bottom surface is in contact with the positioning portion in a height direction from the bottom surface.   5. The optical scanning device according to claim 1, wherein the wall is a wall extending from a side wall of the optical box toward an inside of the optical box. 6.   5. The light according to claim 4, wherein the wall includes a connecting portion that is positioned above the beam splitter in a height direction from the bottom surface of the optical box and connects the wall and the positioning portion. Scanning device.   7. The apparatus according to claim 1, further comprising a control unit configured to control a light amount of the light beam emitted from the light source based on a light amount of the second light beam received by the optical sensor. Optical scanning device. An optical scanning device according to any one of claims 1 to 6,
The photoreceptor;
Developing means for developing the electrostatic latent image formed on the photosensitive member by exposure with the first light beam with toner;
Transfer means for transferring a toner image developed on the photoreceptor onto a recording medium;
An image forming apparatus comprising: a control unit configured to control a light amount of the light beam emitted from the light source based on a light amount of the second light beam received by the optical sensor. A light source that emits a light beam;
A beam splitter that separates a light beam emitted from the light source into a first light beam and a second light beam;
A rotating polygon mirror for deflecting the first light beam so that the first light beam separated by the beam splitter scans on a photoreceptor;
A motor for rotationally driving the rotary polygon mirror;
A first lens for guiding the first light beam deflected by the rotary polygon mirror to the photoconductor;
An optical sensor on which the second light beam reflected by the beam splitter is incident;
The light beam emitted from the light source and incident on the beam splitter is disposed on a line segment on the opposite side of the first lens from the first lens and connecting the beam splitter and the optical sensor. A second lens that is incident on the second light beam separated by the splitter and that focuses the incident second light beam on the optical sensor;
An optical box in which the beam splitter, the first lens, the rotary polygon mirror, the motor, the optical sensor, and the second lens are disposed,
The optical box is erected from the bottom surface of the optical box between the area where the rotary polygon mirror and the motor are arranged and the area where the second lens is arranged, and is on the reflection surface of the rotary polygon mirror. An optical scanning device comprising opposing walls.   The optical scanning device according to claim 9, wherein the wall is a member that suppresses an airflow generated by rotation of the rotary polygon mirror from directly hitting the second lens. The beam splitter is attached to the bottom surface of the optical box,
The beam splitter in a direction parallel to the bottom surface is disposed at a position adjacent to the wall and is in contact with the wall;
11. The optical scanning according to claim 9, wherein the wall and the beam splitter separate an area where the rotary polygon mirror and the motor are arranged from an area where the second lens is arranged. apparatus.   The optical box is positioned from the optical box on the incident surface side of the first lens on which the first light beam deflected by the rotary polygon mirror is incident, and a positioning unit that positions the first lens The optical scanning device according to claim 11, wherein the other end of the beam splitter in a direction parallel to the bottom surface is in contact with the positioning portion in a height direction from the bottom surface.   The optical scanning device according to claim 9, wherein the wall is a wall extending from a side wall of the optical box toward an inside of the optical box.   The light according to claim 12, wherein the wall includes a connecting portion that is positioned above the beam splitter in a height direction from the bottom surface of the optical box and connects the wall and the positioning portion. Scanning device.   15. The control device according to claim 9, further comprising a control unit configured to control a light amount of the light beam emitted from the light source based on a light amount of the second light beam received by the optical sensor. Optical scanning device. An optical scanning device according to any one of claims 9 to 14,
The photoreceptor;
A developing device that develops an electrostatic latent image formed on the photoreceptor by being exposed by the first light beam with toner;
A transfer device for transferring a toner image developed on the photoreceptor onto a recording medium;
An image forming apparatus comprising: a control unit configured to control a light amount of the light beam emitted from the light source based on a light amount of the second light beam received by the optical sensor.